Abstract
Abscisic acid (ABA)-induced foliar senescence was examined using detached leaf segments of light-grown Hordeum vulgare L. cv. Dyan seedlings, incubated with or without exogenous ABA in either total darkness or under continuous illumination. In darkness, the chlorophyll (Chl) content declined rapidly, ABA levels increased sharply whereas carotenoid levels were sustained, and declined gradually during the course of senescence. By comparison, untreated leaf segments exposed to continuous illumination displayed enhanced loss of Chl and carotenoids and slower rates of ABA accumulation. In response to exogenous ABA, Chl and carotenoid content of light-incubated leaf segments declined markedly and the rate of decline increased with an increase in exogenous ABA concentration. In dark-incubated leaf segments, exogenous ABA, in the range 0.1–100 μM, had little or no significant effect on the rate of Chl loss, and calculation of the Chl : carotenoid ratio revealed that dark-incubated leaf segments were insensitive to exogenous ABA. At 1 mM ABA, Chl loss was delayed. It is proposed that the inability of exogenous ABA to accelerate Chl breakdown in dark-incubated leaves was caused by a transient accumulation of carotenoids, and in particular xanthophylls, possibly related to the rapid elevation in endogenous ABA levels. Furthermore, it is suggested that retardation of carotenoid breakdown is a contributing factor accounting for differences in ABA-induced Chl loss between light- and dark-incubated senescing leaves. Die invloed van absissiensuur (ABA) op die veroudering van blaarsegmente van Hordeum vulgare L. cv. Dyan saailinge wat in òf algehele donkerte òf in ononderbroke lig geïnkubeer is, is ondersoek. In die donker het die chlorofil (Chl)-konsentrasie van onbehandelde blaarsegmente vinnig afgeneem, die ABA-konsentrasie het vinnig toegeneem en die karetonoïedkonsentrasie het stadig afgeneem. In onbehandelde blaarsegmente wat in ononderbroke lig geïnkubeer is, het die Chl- en die karetonoïedkonsentrasie vinniger afgeneem en het die ABA-konsentrasie stadiger toegeneem. Na die toevoeging van eksogene ABA aan blaarsegmente wat in ononderbroke lig gehou is, het die Chl- en karetonoïedkonsentrasie vinniger afgeneem hoe hoër die toegediende ABA-konsentrasie was. In die geval van blaarsegmente wat in die donker geïnkubeer is, het eksogeen toegediende ABA tussen 0.1 en 100 μM egter nie ’n betekenisvolle effek op die Chl-konsentrasie of op die Chl : karetonoïed-verhouding gehad nie. Teen ’n konsentrasie van 1 mM ABA is Chl-verlies vertraag. Ons stel voor dat die onvermoë van eksogene ABA om die Chl-afbreking in die donker te versnel, toegeskryf kan word aan die tydelike ophoping van karetonoïede, veral xantofille, wat moontlik verband hou met die vinnige verhoging in eksogene ABA-konsentrasie. Die vertraging in karetonoïedafbreking is ook ’n bydraende faktor wat die verskil in ABA-geïnduseerde Chl-verlies tussen verouderende blaarsegmente in die donker en in lig.
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Claims 12
Claim · model-written summary
In darkness, leaf chlorophyll declined rapidly.
- Taxon
- Hordeum vulgare L.
.jpg?width=60)
Hordeum vulgaree1 - Material
- Dyane1
- Organ / stage
- leafe2
- Outcome
- chlorophyll (Chl) contente0
- Direction
- declined rapidlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“In darkness, the chlorophyll (Chl) content declined rapidly”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
e2“detached leaf segments”
Claim · model-written summary
In darkness, ABA levels increased sharply.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree1
- Material
- Dyane1
- Outcome
- ABA levelse0
- Direction
- increased sharplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA levels increased sharply”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
In darkness, carotenoids were initially sustained and then gradually declined.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree1
- Outcome
- carotenoid levelse0
- Direction
- declined graduallye0
- Qualifier
- during the course of senescencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“carotenoid levels were sustained, and declined gradually during the course of senescence”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Untreated leaves under continuous light lost chlorophyll and carotenoids faster than leaves in darkness.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Treatment
- continuous illuminatione0
- Outcome
- loss of Chl and carotenoidse0
- Direction
- enhancede0
- Comparator
- darknesse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“untreated leaf segments exposed to continuous illumination displayed enhanced loss of Chl and carotenoids”
e1“In darkness, the chlorophyll (Chl) content declined rapidly, ABA levels increased sharply whereas carotenoid levels were sustained”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Untreated illuminated leaves accumulated ABA more slowly than dark leaves.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Treatment
- continuous illuminatione0
- Outcome
- rates of ABA accumulatione0
- Direction
- slowere0
- Comparator
- darknesse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“untreated leaf segments exposed to continuous illumination displayed enhanced loss of Chl and carotenoids and slower rates of ABA accumulation”
e1“In darkness, the chlorophyll (Chl) content declined rapidly”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Exogenous ABA accelerated chlorophyll and carotenoid decline in illuminated leaves, with stronger decline at higher concentrations.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Treatment
- exogenous ABAe0
- Outcome
- Chl and carotenoid contente0
- Direction
- declined markedlye0
- Qualifier
- light-incubated leaf segmentse0
- Comparator
- without exogenous ABAe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In response to exogenous ABA, Chl and carotenoid content of light-incubated leaf segments declined markedly and the rate of decline increased with an increase in exogenous ABA concentration”
e1“incubated with or without exogenous ABA”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Exogenous ABA from 0.1 to 100 μM had little or no significant effect on chlorophyll loss in dark leaves.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Treatment
- exogenous ABA, in the range 0.1–100 μMe0
- Outcome
- rate of Chl losse0
- Direction
- little or no significant effecte0
- Comparator
- without exogenous ABAe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In dark-incubated leaf segments, exogenous ABA, in the range 0.1–100 μM, had little or no significant effect on the rate of Chl loss”
e1“incubated with or without exogenous ABA”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Dark-incubated leaf segments were insensitive to exogenous ABA according to their chlorophyll to carotenoid ratio.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree1
- Outcome
- dark-incubated leaf segments were insensitive to exogenous ABAe0
- Qualifier
- Chl : carotenoid ratioe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“calculation of the Chl : carotenoid ratio revealed that dark-incubated leaf segments were insensitive to exogenous ABA”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
At 1 mM ABA, chlorophyll loss was delayed in dark-incubated leaves.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Treatment
- 1 mM ABAe0
- Outcome
- Chl losse0
- Direction
- delayede0
- Qualifier
- total darknesse1
- Comparator
- without exogenous ABAe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 1 mM ABA, Chl loss was delayed”
e1“incubated with or without exogenous ABA in either total darkness”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Authors proposed that transient carotenoid, especially xanthophyll, accumulation prevented exogenous ABA from accelerating chlorophyll breakdown in dark leaves.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree1
- Outcome
- inability of exogenous ABA to accelerate Chl breakdowne0
- Qualifier
- transient accumulation of carotenoids, and in particular xanthophyllse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inability of exogenous ABA to accelerate Chl breakdown in dark-incubated leaves was caused by a transient accumulation of carotenoids, and in particular xanthophylls”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Authors suggested rapid endogenous ABA elevation might relate to transient xanthophyll accumulation.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree2
- Compound
- endogenous ABAe0
- Outcome
- transient accumulation of carotenoids, and in particular xanthophyllse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“possibly related to the rapid elevation in endogenous ABA levels”
e1“a transient accumulation of carotenoids, and in particular xanthophylls”
e2“light-grown Hordeum vulgare L. cv. Dyan seedlings”
Claim · model-written summary
Authors suggested slower carotenoid breakdown contributes to the difference in ABA-induced chlorophyll loss between illuminated and dark leaves.
- Taxon
- Hordeum vulgare L.Hordeum vulgaree1
- Outcome
- differences in ABA-induced Chl losse0
- Qualifier
- retardation of carotenoid breakdowne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“retardation of carotenoid breakdown is a contributing factor accounting for differences in ABA-induced Chl loss between light- and dark-incubated senescing leaves”
e1“light-grown Hordeum vulgare L. cv. Dyan seedlings”
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12 papers more in this group
See all 16 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.